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AP EAMCET202124 Aug 2021Evening ShiftChemistryThermodynamics (C)Actual

The heat liberated when 1.89 ~g of benzoic acid is burnt in a bomb calorimeter at 25^ C increases the temperature of 18.94 ~kg of water by 0.632^ C . If the specific heat of water at 25^ C is 0.998 cal / ( g ^ C ) , then find the heat of combustion of benzoic acid.

Options

  1. A2540 ~kJ ~mol ⁻¹
  2. B1975 ~kJ ~mol ⁻¹
  3. C3240 ~kJ ~mol ⁻¹
  4. D2825 ~kJ ~mol ⁻¹

Correct answer

C. 3240 ~kJ ~mol ⁻¹

Step-by-step solution

Mass of benzoic acid =1.89 ~g Temperature =25^ C =298 ~K Mass of water =18.94 ~kg Increase in temperature ( t)=0.632^ C Specific heat of H ₂ O =0.998 cal / g ^ C Heat gained by water or heat liberated by benzoic acid (Q)Q=m s t aligned & =18.94 0.998 0.632 & =11.946 kcal =49.982 ~kJ aligned 1.89 ~g of acid, liberates 49.98 ~kJ of heat Heat liberated by 122 ~g of acid = 49.98 122 1.89 =3226.2 ~kJ / mol

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